Lock-nut.



IBVING C. WQODWARD, F CHICAGO, ILLINOYIS.

LOCK-NUT.

To all whom t may concern:

Be it known that I, IRVING C. WoonwAm), a citizen of the United Statesof America, and a resident of Chicago, county of Cook,

and State of Illinois, have invented certain new and useful Improvementsin LockNuts, of which the following is a specification.

. The main Yobjects of this invention are to provide an improved form oflock nut wherein the threads are coated With material adapted andarranged to cause thenut to grip the'threads of the bolt so as toeffectively prevent the nut from accidentally backing off-.or becomingloosened through being jarred and strained in service; and to provide animproved simple and inexpensive method of applying the coating materialto the nut.

An illustrative embodiment of this invention is shown in theaccompanying drawings, in which-' Figure 1 is a sectional View of a nutwith threads suitably coated with material in accordance with thisinvention and showing of threading tap for' also a suitable form shapingthe coated threads so as to accomplish the desired results. Fig. 2'is asectional view of the lock nut in position on a bolt. Fig. 3 is an endview of the special threading tap shown in Fig. 1.

The nut 4 may be of any suitable design with threads out'therein in theusual manner, and with threads of substantially uni- V form shapethroughout. After the threading ofthe nut has been completed, itsthreads are coated with Suitable material applied in such manner as tomake the nut grip the threads of the bolt upon which it is screwed. Forexample, the nut may be dipped into a molten soft metal, such as zinc,to a suitable depth, say about half the thickness of the nut. The moltenmetal adheres to the nut and forms a coating '5 on the threads, somewhatas indicated by the dotted lines 6, Fig. 1. A threading tap 7 is thenrun through the nut 4 so as to cut away the surplus part of the zinccoating 5 and leave a tapering layer thereof on two or more of theoutermost convolutions of the threads.

The threading tap 7 is preferably of special design, being formed withthe usual axially disposed grooves 8 and ridges 9, but the first twoconvolutions 10 of the threads at the end of the tap 7 are of triangularcross section and of the same pitch as the other threads but of smallerdiameter. On

Specification of Letters Patent.

Patented May 4, 1915.

Application led March 25, 1914. Serial No. 827,075.

engaging the coating 5 the threads 10 score the coating in the threadgrooves of the nut so as to facilitate the cutting which is done by thenext three or four threads 11. The

threads 11 are successively and gradually in-` creased in Vdiameter upto the full diameter; of the threads 12 on the body of the tap. Thus asthe tap is driven through the nut 4f, the coating 5 is gradually shavedolf `until there remains onlya tapering layer on the outermost threads,this being thickest at the outer end of the nut and tapering to nothingat a point some distance from the inner end of the nut, say midwaybetween Vthe ends.

When the finished lock nut 4 is screwed onto a bolt, it turns easilyuntil the end of the bolt reaches the coating 5 of soft metal, whereuponmore and more resistance is encountered as the bolt cuts and forces itsway through the gradually thickening layer of the coating. Thus when thenut is screwed home upon the bol the coating lls the entire spacesbetween adjacent threads of the nut and bolt and locks the nut sosecurely that it cannot be accidentally jarred loose or backed oli',although it may be readily removed by the use of a wrench.

I am aware that a construction has been previously proposed wherein `alayer of soft metal is interposed between the threads of a nut and bolt,but in such case the relative diameters of the nut and bolt werenecessarily diferent` than those of standard form to make room for thesoft metal and the holding power consequently was no greater than theshearing strength of the soft metal, rendering the nuts impractical forresisting vibration and steady strain. The present invention isdistinctly diii'erent in that it employs merely a coating applied in apeculiar manner to nuts and bolts which are both of standard form andcapable of bearing all of the load that can be borne -by standard nutsand bolts.

I claim:

1. As an article of manufacture, a standard nut threaded to fit its boltand having its threads adjacentrto one end only coated with materialadapted to rictionally grip the bolt and secure the nut thereon.

2. As an article of manufacture, a standard nut threaded to lit astandard bolt and uhaving a packing of softer metal embedded in aportion only of the thread grooves whereby, when said nut is screwedonto its bolt, the threads of the bolt will be forced to cut into seidsoft nietl coe-,ting and bindk coated with a. tapered layer of softmetal whereby, when said nut. is screwed onto a bolt, the threads w/illbeA forced to cut into metal coating and bind said nut on the bolt.

' l Signed at Chicago this 23d day of March 1914. we is Y IRVNG C.WOODWARD.

Witnesses:

EUGENEA. RUMMLEB, -M. IRENnHUToHnIGs;

